Aim An experimental study into cesium energy pooling collision,Cs(6P3/2)+Cs(6P3/2)→Cs(nLJ=8S1/2,4F5/2,4F7/2)+Cs(6S1/2),has been carried out in a cell.Methods A single mode semiconductor laser is used to excite the 6P3/2 state,the other single mode laser antiparallel to pumping laser is used as absorption line to detect excited atomic intensity and its spatial distribution,with absorption line transiting from 6P3/2 to 8S1/2 and parallel to the movement of pumping laser.The cross section of energy pooling collisions is obtained by the ratio of the excited atomic density to fluorescence intensity of the spectral line.Results The cross sections of 8S1/2,4F5/2 and 4F7/2 are(5.43±1.56)×10-16 cm2,(4.89±1.16)×10-16 cm2 and(6.17±1.60)×10-16 cm2,respectively.Conclusion Compared with other test results,the calculation results are exact.
Aim An experimental study into cesium energy pooling collision,Cs(6P3/2)+Cs(6P3/2)→Cs(nLJ=8S1/2,4F5/2,4F7/2)+Cs(6S1/2),has been carried out in a cell.Methods A single mode semiconductor laser is used to excite the 6P3/2 state,the other single mode laser antiparallel to pumping laser is used as absorption line to detect excited atomic intensity and its spatial distribution,with absorption line transiting from 6P3/2 to 8S1/2 and parallel to the movement of pumping laser.The cross section of energy pooling collisions is obtained by the ratio of the excited atomic density to fluorescence intensity of the spectral line.Results The cross sections of 8S1/2,4F5/2 and 4F7/2 are(5.43±1.56)×10-16 cm2,(4.89±1.16)×10-16 cm2 and(6.17±1.60)×10-16 cm2,respectively.Conclusion Compared with other test results,the calculation results are exact.
Using stepwise excitation of the cesium 8S atoms level in Cs vapor,several collisional and radiative processes have been identified from the intensities and spectra of the Cs fluorescence.The 5D state was populated by 8S→7P→5D transitions.In cesium densities 1016-1017?cm-3,the energy pooling collisions 5D+5D→nL+6S(nL=9D,11S,7F are studied.Since the 5D→6P(3.0-3.6 μm) fluorescence could not be detected with this experiment,the EP rate coefficients have been measured relative to the known rate coefficient of the collision,i.e.,6P+5D→6S+7D.The excited-atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single-mode laser beam,tuned to 6P3/2→8S1/2 transition,which could be translated parallel to the pump beam.The excited atom densities are combined with measured fluorescene ratios to determine cross sections for the cesium energy pooling process.The average values(in units of 10-10?cm3s-1) for nL=9D,11S and 7F are 8.4±4.2,7.3±3.6,and 9.7±4.8,respectively.Influence on k11S and k7F of the energy transfer process 11S+6S7F+6S is also dicussed.
By applying the laser absorption and fluorescence method,the cross sections for the fine structure mixing and quenching of the Cs(6P) state,induced by collision with He atoms,have been measured.Cesium atoms were optically excited to the 6P3/2 state.The excited atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single mode laser beam,which was tuned to the 6PJ→8S1/2 transitions.The effective radiative rates were calculated for the 6PJ→6S transitions.The fluorescence intensity I895 of the sensitized 6P1/2→6S1/2 emission was measured as a function of He density in the range 0.5×1018～4×1018cm-3 at constant temperature T=337 K.It was found that the quantity N/I895 exhibited a parabolic dependence on N,confirming that the quenching of the 6PJ states was due to collision with He atoms,not ground state Cs atoms.The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections σ3/2→1/2=(1.46±0.51)×10-19 cm2 and σD=(2.28±0.80)×10-18 cm2 for the 6PJ fine structure mixing and quenching,respectively,due to collision with He atoms.
An experimental study of energy transfer collisions,Cs(6P3/2)+ Cs(6P3/2)+He→Cs(4FJ)+Cs(6S1/2)+He,in the range 337 K to 357 K,has carried out in a cell.Atoms were excited to the 6P3/2 state using a single-mode diode laser.The Cs(6P3/2) atom density and spatial distribution were mapped by monitoring the absorbion of a counterpropagating laser beam.The buffer gas enhanced the energy transfer between two 6P3/2,which was based on the measurement of the fluorescence from the 4FJ states populated by three-body collision.The three-body collision rate coefficients(in units of 10-27 cm6s-1) for 4F5/2 and 4F7/2 are 1.35±0.18,2.22±0.21,respectively.
An experimental study of energy transfer collisions,Cs$(6P_3/2)$+ Cs$(6P_3/2$)+He→Cs(nl_J)+Cs$(6S_1/2$)+He where $nl_J$=$8S_1/2,4F_5/2$ or $4F_7/2$,in the range 330K to 340K,been carried out in a cell.Atoms were excited to the $6P_3/2$ state using a single-mode diode laser.The Cs$(6P_3/2$) atom density and spatial distribution were mapped by monitoring the absorbion of a counterpropagating laser beam.The buffer gas enhanced the energy transfer between two $6P_3/2$,which was based on the measurement of the fluorescence from the $nl_J$ states populated by three-body collision.The three-body collision rate coefficients(in units of 10~-27cm~6$s~-1)$ for 8$S_1/2,4F_5/2$ and $4F_7/2$ are 1.80±0.72,1.28±0.51 and 2.23±0.89,respectively.
At a Cs density higher than 9 x 10(14) cm(-3), cesium vapor was irradiated in a glass fluorescence cell with pulses of radiation from an YAG-laser-pumped OPO laser, populating 6D(5/2) state by two-photon absorption. Energy transfer in Cs6(D(5/2)) + Cs (6S) collisions was studied using methods of atomic fluorescence. At the different Cs densities, we have measured the time-integrated intensities of the components and fitted a three-state rate equation model to obtain the cross sections. The experimental points were fitted to a straight line very well. The authors converted the gradient and intercept into cross sections. The cross section for 6D(5/2)-->6D(3/2) transfer is (2.1 +/- 0.4) x 10(14) cm2. The cross section for excitation transfer out of the 6D doublet is sigmaQ = (1.6 +/- 0.4) x 10(-14) cm2. The cross section on contains information on reverse energy pooling collisions [i.e., Cs(6D(3/2)) + Cs (6S(1/2))-->Cs(6P) + 6Cs(P)] and contribution from mining in 6Dj-->7P(J'), This latter contribution could be subtracted out using the results of a second experiment. At a Cs density lower than 6.0 x 10(12) cm3, the laser was used to pump the 6D(3/2) and 6D(5/2) states, respectively. The resulting fluorescence included the direct component emitted in the decay of the 6D(J) state and the sensitized component arising from the collisionally populated 7P(J') state. Relative intensities of the components yielded the cross sections. The cross-sections for the processes Cs(6D(5/2)) + Cs(6S(1/2))-->Cs(7P(J')) + Cs(6S(1/2)) are (1.6 +/- 0.5) x 10(-15) cm2. for J'= 3/2 and (6.5 +/- 2.1) x 10(-16) cm2, for J' = 1/2, respectively. The cross-sections for the processes Cs(6D(3/2) + Cs(6S(1/2))-->Cs (7P(J')) + Cs(6S(1/2)) are (1.9 +/- 0.6) x 10(-15) cm2. for J' = 3/2 and (7.6 + 2.4) x 10(-16) cm2, for J' = 1/2, respectively. The 6D(J) -->7P(J'), energy transfer rate coefficient is small. The total quenching rate coefficient out of the 6D(J) state is much larger. Evidence suggests that the quenching of the 6D(J) state is caused predominantly by reverse energy-pooling process. The cross section for this process, i.e., Cs(6D(3/2))+Cs(6S(1/2))-->Cs(6P) + Cs(6P) is (1.3 +/- 0.4) x 10(-14) cm2.
Applying the CW laser absorption and fluorescence method, the cross sections for the fine structure mixing and quenching of the Cs(6P) state, induced by collision with N2 molecules, were measured. Cesium atoms were optically excited to the 6P3/2 state. The excited atom density and spatial distribution were mapped by monitoring the absorption of a counterpropagating single mode laser beam, tuned to the 6P1 --> 8S(1/2) transitions, which could be translated parallel to the pump beam. The transmission factors, which describe the average probability that photons emitted within the fluorescence detection region can pass through the optically thick vapor without being absorbed, were calculated for 6P --> 6S(1/2) transitions. The N2 caused line broadening and therefore increased the effective pumping rate and radiative rates. The effective radiative rates were calculated for the 6P(J) --> 6S transitions. The fluorescence intensity I895 of the sensitized 6P(1/2) --> 6S(1/2) emission was measured as a function of N2 density in the range 2 x 10(16) < N < 1.4 x 10(17) cm(-3) at a constant temperature T = 337 K, which produced cesium density N0 = 1.25 x 10(12) cm(-3). The transparency of the cell was obtained by the absorption of light beam passing the cell. The transparency is not a simple function of N2 density. It was found that the quantity N/I895 (I895 being corrected for the cell transparency) exhibited a parabolic dependence on N, confirming that the quenching of the 6P(J) states is due to collision with N2 molecules instead of Cs ground state atoms. The coefficients of the second-order polynomial fitted through the measured data yielded the cross sections sigma3/2 --> 1/2 = (0.42 +/- 0.17) x 10(-16) cm2 and sigmaD = (1.31 +/- 0.52) x 10(-16) cm2 for the 6P(J) fine-structure mixing and quenching, respectively, due to collision with N2 molecules. The quenching rate coefficient is about 3 times larger than the rate coefficient for the fine-structure mixing. Our values for these cross sections are in agreement, within combined error bars, with the values we have recently obtained under different experimental conditions.